"An alternative to admitting the existence of dark energy is to review the postulates that necessitate its introduction. In particular, it has been proposed that the SNe observations could be accounted for without dark energy if our local environment were emptier than the surrounding Universe, i.e., if we were to live in a void. This explanation for the apparent acceleration does not invoke any exotic substances, extra dimensions, or modifications to gravity – but it does require a rejection of the Copernican Principle. We would be required to live near the center of a spherically symmetric under-density, on a scale of the same order of magnitude as the observable Universe. Such a situation would have profound consequences for the interpretation of all cosmological observations, and would ultimately mean that we could not infer the properties of the Universe at large from what we observe locally.
Within the standard inflationary cosmological model the probability of large, deep voids occurring is extremely small. However, it can be argued that the center of a large underdensity is the most likely place for observers to find themselves. In this case, finding ourselves in the center of a giant void would violate the Copernican principle, that we are not in a special place…"
- “Living in a Void: Testing the Copernican Principle with Distant Supernovae,” Physical Review Letters, 101, 131302 (2008) DOI: 10.1103/PhysRevLett.101.131302.with citation from A. D. Linde, D. A. Linde and A. Mezhlumian in Physical Letters B345, 203 (1995) and S. Alexander, T. Biswas and A. Notari at [arXiv:0712.0370]; and H. Alnes, M. Amarzguioui and Ø. Grøn in Physical Review D73, 083519 (2006); and J. Garcia‐Dellido & T. Jaugboelle in Journal of Cosmology and Astroparticle Physics 04, 003 (2008).
Within the standard inflationary cosmological model the probability of large, deep voids occurring is extremely small. However, it can be argued that the center of a large underdensity is the most likely place for observers to find themselves. In this case, finding ourselves in the center of a giant void would violate the Copernican principle, that we are not in a special place…"
- “Living in a Void: Testing the Copernican Principle with Distant Supernovae,” Physical Review Letters, 101, 131302 (2008) DOI: 10.1103/PhysRevLett.101.131302.with citation from A. D. Linde, D. A. Linde and A. Mezhlumian in Physical Letters B345, 203 (1995) and S. Alexander, T. Biswas and A. Notari at [arXiv:0712.0370]; and H. Alnes, M. Amarzguioui and Ø. Grøn in Physical Review D73, 083519 (2006); and J. Garcia‐Dellido & T. Jaugboelle in Journal of Cosmology and Astroparticle Physics 04, 003 (2008).